That spectrophotometer is an excellent instrument in measuring colour differences even when they can't be appreciated by human eye.
Mainly used to define the ceramic glazes colours, it's very useful in comparing different glazes
because it provides the values of ΔL (if a glaze is clearer or darker than a target), Δa (if a glaze is more red or more green than a target), Δb (if a glaze is more yellow or more blu than a target).